The present invention relates to a catalyst for producing carboxylic acid esters, and more particularly, to a catalyst for producing carboxylic acid esters from aldehydes and alcohols in one-step reaction and a process using such catalyst.
One known process for preparing a carboxylic acid ester from an aldehyde involves first manufacturing a carboxylic acid by oxidizing an aldehyde, and then reacting this carboxylic acid with an alcohol. This process, however, has disadvantages in that it necessitates large equivalent of starting materials since the process involves two-step (oxidation and esterification) reaction operations. Furthermore, the process suffers from poor performance of the catalyst used in the reactions, and the yield of obtained carboxylic acid ester is inadequate.
Several methods have been disclosed with regard to producing high yield carboxylic acid esters in a one-step liquid phase reaction from an aldehyde and an alcohol in the presence of specific catalysts. For example, JP-B-57-135856 proposes Pd and Pb based catalysts using calcium carbonate as a carrier, JP-B-4-72578 proposes Pb based catalysts using zinc oxide as a carrier, JP-A-57-50545 and JP-A-61-243044 propose various types of Pd/Pb based catalysts, JP-B-61-60820 proposes Pd/Bi based catalysts, JP-B-62-7902 and JP-A-5-148184 propose the catalysts composed of Pd and at least one element selected from Pb and Bi, and, JP-B-57-35860 proposes Pd/Tl/Hg based catalysts.
The processes for preparing carboxylic acid ester using aforementioned catalysts, however, have low reaction rates and undesirable by-products.
Thus, further process improvements for preparing a carboxylic acid ester from aldehydes and alcohols are desirable.